valerie

Could some one explain too me what has happened . My son caught 7 roach last autum and put them in our pond 15X5 M size, depth : very shallow to 2 meters deep. Yesterday we found 4 dead. Two frozen and the other two on their side but not frozen. They had grown substantially in the year look very healthey and were all in the order of 1lb in weight. We have had no rain fall this Autume , the water level has droped and we have had three hard frosts minus 7 for three days. No running water enters the pond. What has happened?